Semiconductor device and semiconductor device package including the same

ABSTRACT

A semiconductor device includes a semiconductor structure including a first conductive semiconductor layer, a second conductive semiconductor layer, and an active layer provided between the first conductive semiconductor layer and the second conductive semiconductor layer, and a semiconductor device package including the semiconductor device. The active layer includes a plurality of barrier layers and a plurality of well layers. The second conductive semiconductor layer includes a conductive second semiconductor layer and a conductive first semiconductor layer provided on the conductive second semiconductor layer. The conductive second semiconductor layer has a higher aluminum composition than the well layers, and the conductive first semiconductor layer has a lower aluminum composition than the well layers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119 to KoreanApplication Nos. 10-2016-0112809, filed on Sep. 1, 2016, and10-2016-0163830, filed on Dec. 2, 2016, whose entire disclosures arehereby incorporated by reference.

BACKGROUND 1. Field

Embodiments relate to a semiconductor device and a semiconductor devicepackage including the same.

2. Background

Semiconductor devices including compounds such as GaN and AlGaN havemany merits such as wide and adjustable band gap energy and thus may bevariously used as light emitting devices, light receiving devices,various kinds of diodes, or the like.

In particular, light emitting devices using group III-V or II-VIcompound semiconductors or light emitting devices such as a laser diodemay implement various colors such as red, green, blue, and ultravioletdue to the development of thin film growth technology and devicematerials and implement efficient white light rays by using fluorescentmaterials or combining colors. These light emitting devices also haveadvantages with respect to low power consumption, semi-permanent lifespan, fast response time, safety, and environmental friendlinesscompared to conventional light sources such as a fluorescent lamp, anincandescent lamp, or the like.

In addition, when light receiving devices such as optical detectors orsolar cells are produced using group III-V or II-VI compoundsemiconductors, an optical current is generated by absorbing light invarious wavelength ranges due to development of device materials, andthus light may be used in various wavelength ranges from gamma rays toradio wavelength regions. Also, the light receiving devices have theadvantages of fast response time, stability, environmental friendliness,and ease of adjustment of device materials and may be easily used topower control or microwave circuits or communication modules.

Accordingly, semiconductor devices are being extended and applied to thetransmission modules of optical communication means, light emittingdiode backlights substituted for cold cathode fluorescence lamps (CCFL)forming the backlights of liquid crystal display (LCD) devices, whitelight emitting diode lamps to be substituted for fluorescent bulbs,incandescent bulbs, car headlights, traffic lights, and sensors fordetecting gas or fire. In addition, semiconductor devices may also beextended and applied to high-frequency application circuits or otherpower control devices and communication modules.

In particular, a light emitting device that emits light in anultraviolet wavelength range may be used for curing, medical, andsterilization purposes due to its curing or sterilizing action.

Recently, research on ultraviolet light emitting devices has beenactively conducted, but the ultraviolet light emitting devices aredifficult to vertically realize and also have decreased crystallinityduring the substrate separation process.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments will be described in detail with reference to thefollowing drawings in which like reference numerals refer to likeelements wherein:

FIG. 1 is a diagram of a semiconductor structure according to a firstembodiment of the present disclosure;

FIG. 2 is a graph showing an aluminum composition of the semiconductorstructure according to the first embodiment of the present disclosure;

FIG. 3A is a diagram of a semiconductor structure according to a secondembodiment of the present disclosure;

FIG. 3B is a graph showing an aluminum composition of the semiconductorstructure according to the second embodiment of the present disclosure;

FIG. 4 is a diagram of a semiconductor device according to the firstembodiment of the present disclosure;

FIG. 5 is a diagram of a semiconductor device according to the secondembodiment of the present disclosure;

FIGS. 6A and 6B are plan views of a semiconductor device according to anembodiment of the present disclosure;

FIG. 7 is a diagram of a semiconductor structure grown on a substrate;

FIG. 8 is a diagram illustrating a substrate separation process;

FIG. 9 is a diagram illustrating a semiconductor structure etchingprocess;

FIG. 10 is a diagram showing a manufactured semiconductor device;

FIG. 11 is a diagram of a semiconductor structure according to the thirdembodiment of the present disclosure;

FIG. 12 is a graph showing an aluminum composition of the semiconductorstructure according to the third embodiment of the present disclosure;

FIG. 13 is a secondary ion mass spectrometry (SIMS) graph showing achange in aluminum strength of the semiconductor structure according tothe third embodiment of the present disclosure;

FIG. 14 is a partially enlarged view of FIG. 13;

FIG. 15 is a photograph of the semiconductor structure according to thethird embodiment of the present disclosure;

FIG. 16 is a diagram of a second conductive semiconductor layeraccording to the first embodiment of the present disclosure;

FIG. 17 shows AFM data obtained by measuring the surface of a secondconductive semiconductor layer according to the third embodiment of thepresent disclosure;

FIG. 18 shows AFM data obtained by measuring the surface of a GaN thinfilm;

FIG. 19 shows AFM data obtained by measuring the surface of a fast-grownP—AlGaN layer;

FIG. 20 is a diagram of a semiconductor device according to the thirdembodiment of the present disclosure;

FIG. 21A is a plan view of FIG. 20;

FIG. 21B is a view enlarging portion A of FIG. 20;

FIG. 22 is a plan view illustrating an interface between a secondconductive semiconductor layer and a second electrode;

FIG. 23 is a diagram of a semiconductor device package according to anembodiment of the present disclosure;

FIG. 24 is a plan view of the semiconductor device package according toan embodiment of the present disclosure; and

FIG. 25 is a modification of FIG. 24.

DETAILED DESCRIPTION

The following embodiments may be modified or combined with each other,and the scope of the present disclosure is not limited to theembodiments.

Details described in a specific embodiment may be understood asdescriptions associated with other embodiments unless otherwise statedor contradicted even if there is no description thereof in the otherembodiments.

For example, when features of element A are described in a specificembodiment and features of element B are described in anotherembodiment, an embodiment in which element A and element B are combinedwith each other should be understood as falling within the scope of thepresent disclosure unless otherwise stated or contradicted even if notexplicitly stated.

In the descriptions of embodiments, when an element is referred to asbeing above or under another element, the two elements may be in directcontact with each other, or one or more other elements may be providedbetween the two elements. In addition, the term “above or under” usedherein may represent a downward direction in addition to an upwarddirection with respect to one element.

Hereinafter, example embodiments will be described in detail withreference to the accompanying drawings so that they can be easilypracticed by those skilled in the art to which the present disclosurepertains.

A semiconductor structure according to an embodiment of the presentdisclosure may output light of an ultraviolet wavelength band. Forexample, the semiconductor structure may output light ofnear-ultraviolet wavelengths (UV-A), light of far-ultravioletwavelengths (UV-B), or light of deep-ultraviolet wavelengths (UV-C). Thewavelength range may be determined by the aluminum composition of thesemiconductor structure.

For example, the light of near-ultraviolet wavelengths (UV-A) may havewavelengths ranging from 320 nm to 420 nm, the light of far-ultravioletwavelengths (UV-B) may have wavelengths ranging from 280 nm to 320 nm,and the light of deep-ultraviolet wavelengths (UV-C) may havewavelengths ranging from 100 nm to 280 nm.

FIG. 1 is a diagram of a semiconductor structure according to anembodiment of the present disclosure, and FIG. 2 is a graph showing thealuminum composition of the semiconductor structure according to anembodiment of the present disclosure.

Referring to FIG. 1, a semiconductor device according to an embodimentof the present disclosure includes a semiconductor structure 120A, whichincludes a first conductive semiconductor layer 124, a second conductivesemiconductor layer 127, and an active layer 126 provided between thefirst conductive semiconductor layer 124 and the second conductivesemiconductor layer 127.

The first conductive semiconductor layer 124 may be made of a groupIII-V or group II-VI compound semiconductor and may be doped with afirst dopant. The first conductive semiconductor layer 124 may be madeof a material selected from among semiconductor materials having anempirical formula In_(x1)Al_(y1)Ga_(1-x1-y1)N (0≦x1≦1, 0≦y1≦1, and0≦x1+y1≦1)such as GaN, AlGaN, InGaN, InAlGaN, and so on. Also, the firstdopant may be an n-type dopant such as Si, Ge, Sn, Se, and Te. When thefirst dopant is an n-type dopant, the first conductive semiconductorlayer 124 doped with the first dopant may be an n-type semiconductorlayer.

The active layer 126 is provided between the first conductivesemiconductor layer 124 and the second conductive semiconductor layer127. The active layer 126 is a layer in which electrons (or holes)injected through the first conductive semiconductor layer 124 arecombined with holes (or electrons) injected through the secondconductive semiconductor layer 127. The active layer 126 may transitionto a lower energy level due to recombination between an electron and ahole and generate light having an ultraviolet wavelength.

The active layer 126 may have, but is not limited to, any one of asingle-well structure, a multi-well structure, a single-quantum-wellstructure, a multi-quantum-well (MQW) structure, a quantum dotstructure, or a quantum wire structure. Also, the active layer 126 mayinclude a well layer 126 a, and a barrier layer 126 b, and the barrierlayer 126 b may have a greater energy band gap than the well layer 126a.

The second conductive semiconductor layer 127 may be formed on theactive layer 126 and be made of a group III-V or group II-VI compoundsemiconductor. The second conductive semiconductor layer 127 may also bedoped with a second dopant. The second conductive semiconductor layer127 may be made of a semiconductor material having an empirical formulaIn_(x5)Al_(y2)Ga_(1-x5-y2)N (0≦x5≦1, 0≦y2≦1, and 0≦x5+y2≦1) or amaterial selected from among AlInN, AlGaAs, GaP, GaAs, GaAsP, andAlGaInP. When the second dopant is a p-type dopant such as Mg, Zn, Ca,Sr, and Ba, the second conductive semiconductor layer 127 doped with thesecond dopant may be a p-type semiconductor layer.

The second conductive semiconductor layer 127 may include a conductivefirst semiconductor layer 127 a having a relatively low aluminumcomposition and a conductive second semiconductor layer 127 b having arelatively high aluminum composition.

A blocking layer 129 may be provided between the active layer 126 andthe second conductive semiconductor layer 127. The blocking layer 129may block first carriers supplied from the first conductivesemiconductor layer 124 to the active layer 126 from flowing out to thesecond conductive semiconductor layer 127 and may increase theprobability that first carriers will be recombined with second carriersin the active layer 126. The blocking layer 129 may have a greaterenergy band gap than the active layer 126 and/or the second conductivesemiconductor layer 127.

The blocking layer 129 may be made of a material selected from amongsemiconductor materials having an empirical formulaIn_(x1)Al_(y1)Ga_(1-x1-y1)N (0≦x1≦1, 0≦y1≦1, and 0≦x1+y1≦1), forexample, AlGaN, InGaN, InAlGaN, and so on, but is not limited thereto.In the blocking layer 129, a first layer having a high aluminumcomposition 129 b and a second layer having a low aluminum composition129 a may be alternately provided.

Referring to FIG. 2, the first conductive semiconductor layer 124, thebarrier layer 126 b, the well layer 126 a, the conductive secondsemiconductor layer 127 b, and the conductive first semiconductor layer127 a may be GaN-based semiconductors including aluminum.

The first conductive semiconductor layer 124, the barrier layer 126 b,the well layer 126 a, the conductive second semiconductor layer 127 b,and the conductive first semiconductor layer 127 a may be made of AlGaN,but are not limited thereto.

The conductive second semiconductor layer 127 b may have a thicknessgreater than about 10 nm and less than about 200 nm. When the conductivesecond semiconductor layer 127 b has a thickness less than about 10 nm,it may be difficult for electric current to spread evenly in theconductive second semiconductor layer 127 b, and it also may bedifficult to evenly inject electric current to the area of the topsurface of the semiconductor device. When the conductive secondsemiconductor layer 127 b has a thickness greater than about 200 nm, itis possible for there to be a reduction in injection efficiency forelectric current injected into the active layer 126 due to an increasein resistance.

The conductive second semiconductor layer 127 b may have a higheraluminum composition than the well layer 126 a. In order to generateultraviolet light, the well layer 126 a may have an aluminum compositionranging from about 30% to about 50%. When the conductive secondsemiconductor layer 127 b has a lower aluminum composition than the welllayer 126 a, light extraction efficiency may be reduced because theconductive second semiconductor layer 127 b absorbs light.

The conductive second semiconductor layer 127 b may have an aluminumcomposition ranging from about 40% to about 80%. It is possible toreduce light absorption when the conductive second semiconductor layer127 b has an aluminum composition of 40% or higher and also possible toreduce deterioration of electric current injection efficiency when theconductive second semiconductor layer 127 b has an aluminum compositionof 80% or less. For example, when the well layer 126 a has an aluminumcomposition of 30%, the conductive second semiconductor layer 127 b mayhave an average aluminum composition of 40%.

The conductive first semiconductor layer 127 a may have a lower aluminumcomposition than the well layer 126 a. When the conductive firstsemiconductor layer 127 a has a higher aluminum composition than thewell layer 126 a, the conductive first semiconductor layer 127 a is notsufficiently ohmic with a p-ohmic electrode due to an increase inresistance therebetween, and also electric current injection efficiencyis reduced.

The conductive first semiconductor layer 127 a may have an aluminumcomposition greater than about 1% and less than about 50%. When thealuminum composition is greater than about 50%, the conductive firstsemiconductor layer 127 a may not be sufficiently ohmic with a p-ohmicelectrode. When the aluminum composition is less than about 1%, thealuminum composition is close to a GaN composition, and thus theconductive first semiconductor layer 127 a absorbs light.

The conductive first semiconductor layer 127 a may have a thicknessgreater than about 1 nm and less than about 30 nm. As described above,the conductive first semiconductor layer 127 a may absorb ultravioletlight because the conductive first semiconductor layer 127 a has analuminum composition low enough to be ohmic. Accordingly, it may beadvantageous in terms of optical output power to control the conductivefirst semiconductor layer 127 a to be as thin as possible.

However, when the thickness of the conductive first semiconductor layer127 a is controlled to be 1 nm or less, the conductive firstsemiconductor layer 127 a may not be provided in some sections, and aregion in which the conductive second semiconductor layer 127 b isexposed outside the semiconductor structure 120 may be generated.Accordingly, it is possible for there to be a reduction in injectionefficiency of electric current injected into the semiconductor deviceand an increase in the operating voltage of the semiconductor device.Also, when the thickness is greater than about 30 nm, the absorbedquantity of light is so large that optical output power efficiency maydecrease.

The conductive first semiconductor layer 127 a may include a surfacelayer 127 a-2, and an adjustment layer 127 a-1. The surface layer 127a-2 may be a region that is in contact with a p-ohmic electrode, and theadjustment layer 127 a-1 may be a region that adjusts aluminumcomposition.

The surface layer 127 a-2 may have an aluminum composition greater thanabout 1% and less than about 20%.

When the aluminum composition is greater than or equal to 1%, it ispossible to solve the problem of an excessively increasing lightabsorption rate in the surface layer 127 a-2. When the aluminumcomposition is less than or equal to 20%, it is possible to alleviatethe problem of the reduction in electric current injection efficiencydue to an increase in contact resistance of a second electrode (ap-ohmic electrode).

However, the present disclosure is not limited thereto, and the aluminumcomposition of the surface layer 127 a-2 may be adjusted inconsideration of electric current injection characteristics and lightabsorption rate. Alternatively, the aluminum composition of the surfacelayer 127 a-2 may be adjusted according to optical output power requiredby a product.

For example, when the electric current injection characteristics aremore important than the light absorption rate in products to whichsemiconductor devices are applied, the aluminum composition of thesurface layer 127 a-2 may be adjusted to within the range of about 1% toabout 10%. When optical output power characteristics are more importantthan electrical characteristics in products to which semiconductordevices are applied, the aluminum composition of the surface layer 127a-2 may be adjusted to within the range of about 10% to about 20%.

When the aluminum composition of the surface layer 127 a-2 is greaterthan about 1% and less than about 20%, the operating voltage may deceasedue to a decrease in resistance between the surface layer 127 a-2 andthe second electrode. Accordingly, it is possible to enhance theelectrical characteristics. The surface layer 127 a-2 may have athickness greater than about 1 nm and less than about 10 nm.Accordingly, it is possible to alleviate the light absorption problem.

The conductive first semiconductor layer 127 a may have a smallerthickness than the conductive second semiconductor layer 127 b. Thethickness ratio of the conductive first semiconductor layer 127 a to theconductive second semiconductor layer 127 b may range from 1:1.5 to 1:20.When the thickness ratio is 1:1.5 or greater (for example, 1:1.6), itis possible to improve the electric current injection efficiency byachieving a sufficient thickness for the conductive second semiconductorlayer 127 b. When the thickness ratio is 1:20 or less, it is possible toalleviate the problem of ohmic reliability being reduced due to aninsufficient thickness of the conductive first semiconductor layer 127a.

The aluminum composition of the conductive second semiconductor layer127 b may decrease with a second slope L2 as the conductive secondsemiconductor layer 127 b gets farther away from the active layer 126.Also, the aluminum composition of the conductive second semiconductorlayer 127 b may decrease with a first slope L1 as the conductive secondsemiconductor layer 127 b gets farther away from the active layer 126.Accordingly, the aluminum composition of the surface layer 127 a-2 maysatisfy the range of about 1% to about 20%.

However, the present disclosure is not limited thereto, and the aluminumcompositions of the conductive second semiconductor layer 127 b and theconductive first semiconductor layer may not continuously decrease butmay include some sections in which there is no decrease.

In this case, the conductive first semiconductor layer 127 a may have agreater aluminum reduction than the conductive second semiconductorlayer 127 b. That is, the first slope L1 may be greater than the secondslope L2. Here, the slope may be determined on the basis ofsemiconductor layer thickness and aluminum reduction.

The conductive second semiconductor layer 127 b is thicker and has asmaller change in aluminum composition than the conductive firstsemiconductor layer 127 a. Thus, the second slope L2 may be relativelygentle.

However, the conductive first semiconductor layer 127 a is thin and hasa large change in aluminum composition. Thus, the first slope L1 may berelatively steep.

FIG. 3A is a diagram of a semiconductor structure according to anotherembodiment of the present disclosure, and FIG. 3B is a graph showingaluminum composition according to another embodiment of the presentdisclosure.

Referring to FIGS. 3A and 3B, a semiconductor device according to anembodiment of the present disclosure includes a semiconductor structure120B, which includes a first conductive semiconductor layer 124, asecond conductive semiconductor layer 127, an active layer 126 betweenthe first conductive semiconductor layer 124 and the second conductivesemiconductor layer 127, and a third conductive semiconductor layer124-1 provided on the second conductive semiconductor layer 127.

The second conductive semiconductor layer 127 may have a thicknessgreater than about 20 nm and less than about 200 nm. When the secondconductive semiconductor layer 127 has a thickness less than about 20nm, it is possible for there to be a reduction in electric currentinjection efficiency because of an increase in resistance. When thesecond conductive semiconductor layer 127 has a thickness greater thanabout 200 nm, it is possible for there to be a deterioration incrystallinity and an increase in the probability that light emitted bythe active layer 126 will be absorbed because of the excessive thicknessof the second conductive semiconductor layer 127.

The second conductive semiconductor layer 127 may have an aluminumcomposition greater than about 40% and less than about 80%. When thealuminum composition of the second conductive semiconductor layer 127 isless than about 40%, light may be absorbed. When the aluminumcomposition of the second conductive semiconductor layer 127 is greaterthan about 80%, crystallinity may be bad, and electric current injectionefficiency may be insufficient.

The third conductive semiconductor layer 124-1 may have an aluminumcomposition greater than about 1% and less than about 60%. The thirdconductive semiconductor layer 124-1 may be doped with an n-type dopantand may have the same polarity as the first conductive semiconductorlayer 124. For example, the first and third conductive semiconductorlayers 124 and 124-1 may be made of n-AlGaN. In this case, the secondconductive semiconductor layer 127 may be made of P—AlGaN doped with ap-type dopant.

Since electrical characteristics are better between the third conductivesemiconductor layer 124-1 and the second electrode (the ITO) thanbetween the second conductive semiconductor layer 127 and the secondelectrode (the ITO), the aluminum composition of the second conductivesemiconductor layer 127 may be controlled to be higher than that of thewell layer 126 a. Accordingly, it is possible to reduce absorbed lightand enhance optical output power.

The third conductive semiconductor layer 124-1 may have a thickness lessthan about 10 nm. When the third conductive semiconductor layer 124-1has a thickness greater than about 10 nm, the tunneling effect may beweakened. Accordingly, it is possible for there to be a reduction in theefficiency with which second carriers are injected to the active layer126 through the second conductive semiconductor layer 127. Accordingly,the third conductive semiconductor layer 124-1 may have a smallerthickness than the second conductive semiconductor layer 127.

FIG. 4 is a view of a semiconductor device according to an embodiment ofthe present disclosure.

Referring to FIG. 4, the structure that has been described withreference to FIGS. 1 and 2 may be applied to a semiconductor structure120. A recess 128 may be provided in the bottom surface of the secondconductive semiconductor layer 127 and also in a portion of the firstconductive semiconductor layer 124 through the active layer 126.

A first conductive layer 165 includes a connection electrode 167provided in the recess 128 and electrically connected to the firstconductive semiconductor layer 124. A first electrode 142 may beprovided between the connection electrode 167 and the first conductivesemiconductor layer 124. The first electrode 142 may be an ohmicelectrode.

The distance between the top surface of the recess 128 and the topsurface of the semiconductor structure may range from about 1 μm toabout 4 μm. When the distance between the top surface of thesemiconductor structure and the top surface of the recess 128 is lessthen 1 μm, it is possible for there to be a reduction in reliability ofan emitting device. When the distance is greater than about 4 μm, it ispossible for there to be a reduction in light extraction efficiency dueto defects of the crystal provided inside the semiconductor structure orthe like.

A second conductive layer 150 may be provided under and electricallyconnected to the conductive first semiconductor layer. The secondconductive layer 150 may be provided between a plurality of connectionelectrodes 167. The second conductive layer 150 may be partially exposedand electrically connected to a second electrode pad 166.

A second electrode 246 may be provided between and electricallyconnected to the second conductive layer 150 and the conductive firstsemiconductor layer 127 a. The surface layer of the conductive firstsemiconductor layer 127 a may have a relatively low aluminum compositionand thus facilitate an ohmic connection. The conductive firstsemiconductor layer 127 a has a thickness greater than about 1 nm andless than about 30 nm and thus may have low light absorption.

The first conductive layer 165 and the second conductive layer 150 maybe made of a transparent conductive oxide (TCO). The transparentconductive oxide may be selected from among an indium tin oxide (ITO),an indium zinc oxide (IZO), an aluminum zinc oxide (AZO), an aluminumgallium zinc oxide (AGZO), an indium zinc tin oxide (IZTO), an indiumaluminum zinc oxide (IAZO), an indium gallium zinc oxide (IGZO), anindium gallium tin oxide (IGTO), an antimony tin oxide (ATO), a galliumzinc oxide (GZO), an IZO nitride (IZON), ZnO, IrO_(x), RuO_(x), and NiO.

The first conductive layer 165 and the second conductive layer 150 mayinclude an opaque metal such as Ag, Ni, Al, Rh, Pd, Ir, Ru, Mg, Zn, Pt,Au, and Hf. The first conductive layer 165 may be formed in single ormultiple layers in which a TCO and an opaque metal are mixed, but is notlimited thereto.

An insulation layer 130 may be made of at least one material selectedfrom a group consisting of SiO₂, Si_(x)O_(y), Si₃N₄, Si_(x)N_(y),SiO_(x)N_(y), Al₂O₃, TiO₂, and AlN, but is not limited thereto. Theinsulation layer 130 may electrically insulate the connection electrodefrom the active layer 126 and the second conductive semiconductor layer127.

FIG. 5 is a view of a semiconductor device according to anotherembodiment of the present disclosure.

The configuration of the semiconductor structure 120 that has beendescribed with reference to FIG. 1 or FIG. 3 may be applied to thesemiconductor structure 120 of FIG. 5. For example, FIG. 5 shows asemiconductor structure 120A according to the configuration of FIG. 1.

The first electrode 142 may be provided on top of the recesses 128 andelectrically connected with the first conductive semiconductor layer124. A second electrode 246 may be formed under the second conductivesemiconductor layer 127.

The second electrode 246 may be brought into contact with andelectrically connected to the 2-1 conductive semiconductor layer 127 a.

Since the 2-1 conductive semiconductor layer 127 a in contact with thesecond electrode 246 may have an aluminum composition of 1% to 20%, itmay thus facilitate an ohmic connection with the second electrode 246.Also, the conductive first semiconductor layer 127 a has a thicknessgreater than about 1 nm and less than about 30 nm and thus may have lowlight absorption.

Both the first electrode 142 and the second electrode 246 may be anohmic electrode. Both the first electrode 142 and the second electrode246 may be made of at least one of indium tin oxide (ITO), indium zincoxide (IZO), indium zinc tin oxide (IZTO), indium aluminum zinc oxide(IAZO), indium gallium zinc oxide (IGZO), indium gallium tin oxide(IGTO), aluminum zinc oxide (AZO), antimony tin oxide (ATO), galliumzinc oxide (GZO), IZO nitride (IZON), Al-Ga ZnO (AGZO), In-Ga ZnO(IGZO), ZnO, IrOx, RuOx, NiO, RuOx/ITO, Ni/IrOx/Au, Ni/IrOx/Au/ITO, Ag,Ni, Cr, Ti, Al, Rh, Pd, Ir, Sn, In, Ru, Mg, Zn, Pt, Au, and Hf, but isnot limited thereto.

A second electrode pad 166 may be provided in an edge of thesemiconductor device. Since the second electrode pad 166 is provided ina region from which a first insulation layer 131 and a passivation layer180 are partially removed, the second electrode pad 166 may have arecessed central portion and also have a top surface having a concaveportion and a convex portion. A wire (not shown) may be bonded to theconcave portion of the top surface. Accordingly, since the bonding areaincreases, the second electrode pad 166 may be strongly bonded to thewire.

The second electrode pad 166 may serve to reflect light. Thus, as thesecond electrode pad 166 gets closer to the semiconductor structure 120,it is possible to enhance light extraction efficiency.

The convex portion of the second electrode pad 166 may be higher thanthe active layer 126. Accordingly, the second electrode pad 166 mayenhance light extraction efficiency and control the beam angle byupwardly reflecting light emitted from the active layer 126 in adirection horizontal to the device.

The first insulation layer 131 is partially opened under the secondelectrode pad 166 so that the second conductive layer 150 and the secondelectrode may be electrically connected to each other. The passivationlayer 180 may be formed on top of and on the side of the semiconductorstructure 120. The passivation layer 180 may be in contact with a regionadjacent to the second electrode 246 or to the first insulation layerunder the second electrode 246.

The opened part of the first insulation layer 131 where the secondelectrode pad 166 is in contact with the second conductive layer 150 mayhave a width d22 ranging, for example, from about 40 μm to about 90 μm.When the opened part has a width less than about 40 μm, the operatingvoltage may increase. When the opened part has a width greater thanabout 90 μm, it may be difficult to secure a processing margin forpreventing exposure of the second conductive layer 150 to the outside.When the second conductive layer 150 is exposed outside the secondelectrode 246, it is possible for there to be reduction in reliabilityof the device. Accordingly, the width d22 may preferably range from 60%to 95% of the entire width of the second electrode pad 166.

The first insulation layer 131 may electrically insulate the firstelectrode 142 from the active layer 126 and the second conductivesemiconductor layer 127. Also, the first insulation layer 131 mayelectrically insulate the second electrode 246 and the second conductivelayer 150 from the first conductive layer 165.

The first insulation layer 131 may be made of at least one materialselected from the group consisting of SiO₂, Si_(x)O_(y), Si₃N₄,Si_(x)N_(y), SiO_(x)N_(y), Al₂O₃, TiO₂, and AlN, but is not limitedthereto. The first insulation layer 131 may be formed in single ormultiple layers. For example, the first insulation layer 131 may be adistributed Bragg reflector (DBR) having a multi-layered structureincluding an Si oxide or a Ti compound. However, the present disclosureis not limited thereto, and the first insulation layer 131 may includevarious reflective structures.

When the first insulation layer 131 has a reflective function, the firstinsulation layer 131 may upwardly reflect light emitted horizontallyfrom the active layer 126, thereby enhancing light extractionefficiency. As described below, the light extraction efficiency mayincrease as the recesses 128 in an ultraviolet semiconductor deviceincrease in number

The second conductive layer 150 may be provided under the secondelectrode 246. Accordingly, the second electrode pad 166, the secondconductive layer 150, and the second electrode 246 may form oneelectrical channel.

Also, the second conductive layer 150 may entirely surround the secondelectrode 246 and may be in contact with the side surface and the topsurface of the first insulation layer 131. The second conductive layer150 may be made of a material having good adhesion to the firstinsulation layer 131 and may also be made of at least one materialselected from a group consisting of Cr, Al, Ti, Ni, and Au or an alloythereof. The second conductive layer 150 may be made in single ormultiple layers.

When the second conductive layer 150 is in contact with the side surfaceand the top surface of the first insulation layer 131, it is possible toenhance the thermal and electrical reliability of the second electrode246. Also, the second conductive layer 150 may have a reflectivefunction for upwardly reflecting light emitted from a gap between thefirst insulation layer 131 and the second electrode 246.

The second conductive layer 150 may also be provided a second separationdistance, that is, provided in a region where the second conductivesemiconductor layer is exposed between the first insulation layer 131and the second electrode 246. The second conductive layer 150 may beprovided in contact with a side surface and the top surface of thesecond electrode 246 and the side surface and the top surface of thefirst insulation layer 131 at the second separation distance.

Also, a region where a Schottky junction is formed by the secondconductive semiconductor layer 127 coming into contact with the secondconductive layer 150 may be provided within the second separationdistance. By forming the Schottky junction, it is possible to facilitatedistribution of electric current.

The second insulation layer 132 may electrically insulate the secondelectrode 246 and the second conductive layer 150 from the firstconductive layer 165. The first conductive layer 165 may be electricallyconnected to the first electrode 142 via the second insulation layer132.

The first conductive layer 165 and a junction layer 160 may be providedaccording to the bottom surface of the semiconductor structure 120 andthe shape of the recesses 128. The first conductive layer 165 may bemade of a material having good reflectivity. For example, the firstconductive layer 165 may include aluminum. When the first conductivelayer 165 includes aluminum, the first conductive layer 165 may serve toupwardly reflect light emitted by the active layer 126, therebyenhancing light extraction efficiency.

The junction layer 160 may include a conductive material. For example,the junction layer 160 may include a material selected from a groupconsisting of gold, tin, indium, aluminum, silicon, silver, nickel, andcopper or an alloy thereof.

A substrate 170 may be made of a conductive material. For example, thesubstrate 170 may include a metal or a semiconductor material. Forexample, the substrate 170 may be made of a metal having good electricalconductivity and/or thermal conductivity. In this case, heat generatedwhile the semiconductor device operates may be quickly released to theoutside.

The substrate 170 may include a material selected from a groupconsisting of silicon, molybdenum, tungsten, copper, and aluminum or analloy thereof.

A square wave pattern may be formed on top of the semiconductorstructure 120. The square wave pattern may enhance the extractionefficiency of light emitted from the semiconductor structure 120. Thesquare wave pattern may have a different average height depending onultraviolet wavelengths. For UV-C, the average height ranges from about300 nm to about 800 nm. When the height ranges from about 500 nm toabout 600 nm, it is possible to enhance light extraction efficiency.

FIGS. 6A and 6B are plan views of a semiconductor device according to anembodiment of the present disclosure.

When the semiconductor structure 120 has an increasing aluminumcomposition, it is possible for there to be a reduction in electriccurrent spreading characteristics in the semiconductor structure 120.Also, the active layer 126 may have an increasing quantity of lightemitted to the side relative to a GaN-based blue light emitting device(TM mode). The TM mode may be performed by an ultraviolet semiconductordevice.

According to an embodiment of the present disclosure, a larger number ofrecesses 128 may be formed on a GaN semiconductor that emits lighthaving an ultraviolet wavelength band than on a GaN semiconductor thatemits blue light, and then the first electrode 142 may be provided ineach of the recesses 128.

Referring to FIG. 6A, when aluminum composition increases, electriccurrent distribution characteristics may be weakened. Accordingly, anelectric current may be distributed only to points adjacent to the firstelectrode 142, and electric current density may rapidly decrease atpoints apart from the first electrode 142. Accordingly, it is possiblefor an effective light emitting region C2 to become narrow. A region upto a boundary having an electric current density of 40% or less withrespect to a point adjacent to the first electrode 142 and having thehighest electric current density may be defined as the effective lightemitting region C2. For example, the effective light emitting region C2may be adjusted in the range of about 5 μm to about 40 μm from thecenter of each of the recesses 128 depending on the injected electriccurrent level and aluminum composition.

In particular, a low electric current density region C3, which is aregion between adjacent first electrodes 142, has a low electric currentdensity and thus hardly contributes to light emission. Accordingly,according to an embodiment of the present disclosure, a first electrode142 may be additionally provided in the low electric current densityregion C3, which has a low electric current density, thereby enhancingoptical output power.

Generally, since a GaN semiconductor layer has relatively good electriccurrent distribution characteristics, it is preferable that the areas ofthe recesses 128 and the first electrodes 142 be minimized. This isbecause the area of the active layer 126 decreases as the areas of therecess 128 and the first electrode 142 increase. However, according toan embodiment of the present disclosure, the GaN semiconductor layer haslower electric current distribution characteristics than a semiconductordevice that emits blue light because of a high aluminum composition.Accordingly, it may be preferable to reduce size of the low electriccurrent density region C3 by increasing the number of first electrodes142 while reducing the area of the active layer 126.

Referring to FIG. 6B, when the number of recesses 128 is 48, therecesses 128 cannot be straightly arranged in a horizontal or verticaldirection and may be arranged in a zigzag form. In this case, since thearea of the low electric current density region C3 is further decreased,most of the active layer may participate in light emission. When thenumber of recesses 128 ranges from about 70 to about 110, an electriccurrent may be efficiently distributed. Thus, it is possible toadditionally decrease operating voltage and enhance optical outputpower. For a semiconductor device that emits UV-C light, when the numberof recesses 128 is less than about 70, it is possible to reduceelectrical characteristics and optical characteristics. When the numberof recesses 128 is greater than about 110, it is possible to enhanceelectrical characteristics, but there may be a reduction in opticalcharacteristics due to the reduction in volume of the light emittinglayer.

A first area in which a plurality of first electrodes 142 are in contactwith the first conductive semiconductor layer 124 may range from about7.4% to about 20% or from about 10% to about 20% of the maximumhorizontal sectional area of the semiconductor structure 120. The firstarea may be the sum of areas in which the first electrodes 142 are incontact with the first conductive semiconductor layer 124.

When the first area of the plurality of first electrodes 142 is greaterthan or equal to 7.4% of the maximum horizontal sectional area of thesemiconductor structure 120, it is possible to have sufficient electriccurrent distribution characteristics and enhance optical output power.When the first area is less than or equal to 20% of the maximumhorizontal sectional area of the semiconductor structure 120, it ispossible to improve optical output power and operating voltagecharacteristics by securing areas of the active layer and the secondelectrodes.

Also, the total area of the plurality of recesses 128 may range from 13%to 30% of the maximum horizontal sectional area of the semiconductorstructure 120. When the total area of the recesses 128 does not fallwithin this range, it may be difficult to keep the total area of thefirst electrode 142 within the range of about 7.4% to about 20%. Also,this may cause an increase in operating voltage and a decrease inoptical output power.

A second area in which the second electrode 246 is in contact with thesecond conductive semiconductor layer 127 may range from about 35% toabout 70% of the maximum horizontal sectional area of the semiconductorstructure 120. The second area may be the total area in which the secondelectrode 246 is in contact with the second conductive semiconductorlayer 127.

When the second area is greater than or equal to 35%, it is possible toensure the area of the second electrode and thus to enhance injectionefficiency for second carriers and enhance operating voltagecharacteristics. Also, when the second area is less than or equal to70%, it is possible to effectively widen the first area and thus improveinjection efficiency for first carriers.

The first area is inversely proportional to the second area. That is,when the number of recesses is increased to increase the number of firstelectrodes, the area of the second electrode decreases. In order toincrease optical output power, the first carriers should be balancedwith the second carriers. Thus, it is important to determine anappropriate ratio between the first area and the second area.

Accordingly, in order to control the first carriers and the secondcarriers injected into the active layer 126 through an appropriate ratiobetween the first area and the second area, a ratio of the first area inwhich the plurality of first electrodes are in contact with the firstconductive semiconductor layer to the second area in which the secondelectrode is in contact with the second conductive semiconductor layer(i.e., the first area: the second area) may range from 1:3 to 1:10.

FIG. 7 is a diagram of a semiconductor structure grown on a substrate,FIG. 8 is a diagram illustrating a substrate separation process, FIG. 9is a diagram illustrating a semiconductor structure etching process, andFIG. 10 is a diagram showing a manufactured semiconductor device.

Referring to FIG. 7, a buffer layer 122, a light absorption layer 123, afirst conductive semiconductor layer 124, an active layer 126, a secondconductive semiconductor layer 127, a second electrode 246, and a secondconductive layer 150 may be sequentially formed on a growth substrate121.

The light absorption layer 123 includes a first light absorption layer123 a having a low aluminum composition and a second light absorptionlayer 123 b having a high aluminum composition. A plurality of firstlight absorption layers 123 a and a plurality of second light absorptionlayers 123 b may be alternately provided.

The first light absorption layer 123 a may have a lower aluminumcomposition than the first conductive semiconductor layer 124. The firstlight absorption layer 123 a may be separated when absorbing laser lightduring a laser lift-off (LLO) process. Accordingly, it is possible toremove the growth substrate.

The thickness and aluminum composition of the first light absorptionlayer 123 a may be appropriately adjusted to absorb laser light having apredetermined wavelength (e.g., 246 nm). The first light absorptionlayer 123 a may have an aluminum composition ranging from about 20% toabout 50% and a thickness ranging from about 1 nm to about 10 nm. Forexample, the first light absorption layer 123 a may be made of AlGaN,but is not limited thereto.

The second light absorption layer 123 b may have a higher aluminumcomposition than the first conductive semiconductor layer 124.Accordingly, it is possible to enhance crystallinity of the firstconductive semiconductor layer 124, which is grown on the lightabsorption layer 123, because a total aluminum composition decreased bythe first light absorption layer 123 a is increased by the second lightabsorption layer 123 b.

For example, the second light absorption layer 123 b may have analuminum composition ranging from about 60% to about 100% and athickness ranging from about 0.1 nm to about 2.0 nm. The second lightabsorption layer 123 b may be made of AlGaN or AlN.

In order to absorb laser light of 246 nm wavelength, the first lightabsorption layer 123 a may be thicker than the second light absorptionlayer 123 b. The thickness of the first light absorption layer 123 a mayrange from about 1 nm to about 10 nm, and the thickness of the secondlight absorption layer 123 b may range from about 0.5 nm to about 2.0nm.

The thickness ratio of the first light absorption layer 123 a to thesecond light absorption layer 123 b may range from 2:1 to 6:1. When thethickness ratio is less than 2:1, the first light absorption layer 123 ais so thin that laser light cannot be sufficiently absorbed. When thethickness ratio is greater than 6:1, the second light absorption layer123 b is so thin that the total aluminum composition of the lightabsorption layer may be reduced.

The light absorption layer may have a total thickness greater than about100 nm and less than about 400 nm. When the thickness is less than about100 nm, the first light absorption layer 123 a is so thin that it isdifficult to absorb 246 nm laser light. When the thickness is greaterthan about 400 nm, the total aluminum composition is reduced and thuscrystallinity deteriorates.

According to an embodiment of the present disclosure, it is possible toenhance crystallinity by forming the light absorption layer 123 to havea superlattice structure. Due to such a structure, the light absorptionlayer 123 may function as a buffer layer for alleviating a latticemismatch between the growth substrate 121 and the semiconductorstructure 120.

Referring to FIG. 8, a step of removing the growth substrate 121 mayinclude separating the growth substrate 121 by emitting laser L1 fromthe side where the growth substrate 121 is present. The laser L1 mayhave a wavelength band absorbable by the first light absorption layer123 a. As an example, the laser may be a KrF laser having a wavelengthband of 248 nm.

The growth substrate 121 and the second light absorption layer 123 bhave high energy band gaps and thus do not absorb laser L1. However, thefirst light absorption layer 123 a having a low aluminum composition maybe disassembled by absorbing laser L1. Accordingly, it is possible toseparate the first light absorption layer 123 a together with the growthsubstrate 121.

Subsequently, a residual light absorption layer 123-2 on the firstconductive semiconductor layer 124 may be removed through a labelingprocess.

Referring to FIG. 9, after the second conductive layer 150 is formedover the second conductive semiconductor layer 127, a plurality ofrecesses 128 may be formed to pass through up to a portion of the firstconductive semiconductor layer 124 of the semiconductor structure 120.Subsequently, an insulation layer 130 may be formed at the side of eachof the recesses 128 and over the second conductive semiconductor layer127. Subsequently, a first electrodes 142 may be formed on the firstconductive semiconductor layer 124 exposed by each of the recesses 128.

Referring to FIG. 10, a first conductive layer 165 may be formed underthe insulation layer 130. The first conductive layer 165 may beelectrically insulated from the second conductive layer 150 by theinsulation layer 130.

Subsequently, a conductive substrate 170 may be formed under the firstconductive layer 165, and a second electrode pad 166 may be formed on aportion of the second conductive layer 150 that is exposed through amesa etching process.

FIG. 11 is a diagram of a semiconductor structure according to the thirdembodiment of the present disclosure, and FIG. 12 is a graph showing analuminum composition of the semiconductor structure according to thethird embodiment of the present disclosure

Referring to FIG. 11, a semiconductor device according to the embodimentincludes a semiconductor structure 120 including a first conductivesemiconductor layer 124, a second conductive semiconductor layer 127,and an active layer 126 provided between the first conductivesemiconductor layer 124 and the second conductive semiconductor layer127.

The first conductive semiconductor layer 124 may include a conductivefirst semiconductor layer 124 a, a conductive second semiconductor layer124 c, and an intermediate layer 124 b provided between the conductivefirst semiconductor layer 124 a and the conductive second semiconductorlayer 124 c.

The conductive second semiconductor layer 124 c may be provided closerto the active layer 126 than the conductive first semiconductor layer124 a. The conductive second semiconductor layer 124 c may have a loweraluminum composition than the conductive first semiconductor layer 124a. The aluminum composition of the conductive second semiconductor layer124 c may range from about 40% to about 70%, and the aluminumcomposition of the conductive first semiconductor layer 124 a may rangefrom about 50% to about 80%.

The conductive second semiconductor layer 124 c may be thinner than theconductive first semiconductor layer 124 a. The conductive firstsemiconductor layer 124 a may have a thickness ranging from about 130%to about 500% of the thickness of the conductive second semiconductorlayer 124 c. When the thickness of the conductive first semiconductorlayer 124 a is smaller than about 130% of the thickness of theconductive second semiconductor layer 124 c, the intermediate layer 124b provided on the conductive first semiconductor layer 124 a, theconductive second semiconductor layer 124 c, or the like may havereduced crystallinity. When the thickness of the conductive firstsemiconductor layer 124 a is greater than about 150%, the semiconductorstructure is thick enough to cause stress to be applied to thesemiconductor structure that is high enough to crack the semiconductorstructure or change the wavelength of emitted light. According to such aconfiguration, the intermediate layer 124 b is formed after theconductive first semiconductor layer 124 a, which has a high aluminumcomposition, is sufficiently grown. Accordingly, it is possible toenhance the overall crystallinity of the semiconductor structure 120 andalso adjust the wavelength of emitted light according to the user'sdesire.

The intermediate layer 124 b may have a smaller aluminum compositionthan the first conductive semiconductor layer 124. The intermediatelayer 124 b may serve to absorb laser light emitted to the semiconductorstructure during an LLO process to prevent damage to the active layer126. Accordingly, the semiconductor device according to an embodiment ofthe present disclosure can reduce damage to the active layer, therebyenhancing optical power and electrical characteristics.

The thickness and aluminum composition of the intermediate layer 124 bmay be appropriately adjusted to absorb laser light emitted to thesemiconductor structure 120 during an LLO process. For example, theintermediate layer 124 b may have an aluminum composition ranging fromabout 30% to about 60% and a thickness ranging from about 1 nm to about10 nm. For example, the intermediate layer 124 b may be made of AlGaN,but is not limited thereto.

The intermediate layer 124 b may be provided between the firstconductive semiconductor layer 124 and the active layer 126. Also, theintermediate layer 124 b may include a first intermediate layer having alower aluminum composition than the first conductive semiconductor layer124 and a second intermediate layer having a higher aluminum compositionthan the first conductive semiconductor layer 124. A plurality of firstintermediate layers and a plurality of second intermediate layers may bealternately provided.

The active layer 126 may be provided between the first conductivesemiconductor layer 124 and the second conductive semiconductor layer127. The active layer 126 is a layer in which electrons (or holes)injected through the first conductive semiconductor layer 124 arecombined with holes (or electrons) injected through the secondconductive semiconductor layer 127.

The second conductive semiconductor layer 127 may be formed on theactive layer 126 may be made of a group III-V or group II-VI compoundsemiconductor and may also be doped with a second dopant. The secondconductive semiconductor layer 127 may be made of a semiconductormaterial having an empirical formula In_(x5)Al_(y2)Ga_(1-x5-y2)N(0≦x5≦1, 0≦y2≦1, and 0≦x5+y2≦1) or a material selected from among AlInN,AlGaAs, GaP, GaAs, GaAsP, and AlGaInP. When the second dopant is ap-type dopant such as Mg, Zn, Ca, Sr, and Ba, the second conductivesemiconductor layer 127 doped with the second dopant may be a p-typesemiconductor layer.

The second conductive semiconductor layer 127 may include a conductivefirst semiconductor layer 127 a, a conductive second semiconductor layer127 b, and a conductive third semiconductor layer 127 c. The conductivefirst semiconductor layer 127 a may have a lower aluminum compositionthan the conductive second semiconductor layer 127 b.

A blocking layer 129 may be provided between the active layer 126 andthe second conductive semiconductor layer 127. The blocking layer 129may block first carriers (e.g., electrons) supplied from the firstconductive semiconductor layer 124 from flowing out to the secondconductive semiconductor layer 127.

Referring to FIG. 12, the first conductive semiconductor layer 124, theactive layer 126, the second conductive semiconductor layer 127, and theblocking layer 129 may all include aluminum. Accordingly, the firstconductive semiconductor layer 124, the active layer 126, the secondconductive semiconductor layer 127, and the blocking layer 129 may havean AlGaN composition.

The blocking layer 129 may have an aluminum composition ranging fromabout 50% to about 100%. When the aluminum composition of the blockinglayer 129 is less than about 50%, an energy barrier for blockingelectrons may be insufficient in height, and the blocking layer 129 mayabsorb light emitted from the active layer 126.

The blocking layer 129 may include a first section 129 a and a secondsection 129 c. The blocking layer 129 may include a second dopant. Thesecond dopant may include a p-type dopant such as Mg, Zn, Ca, Sr, andBa. When the blocking layer 129 includes a second dopant, the blockinglayer 129 may include a dopant that is identical to that of the secondconductive semiconductor layer. However, the present disclosure is notlimited thereto, and the blocking layer 129 may have the same polarityas the second conductive semiconductor layer 127 and may include asecond dopant that is different from that of the second conductivesemiconductor layer. By using the first section 129 a and the secondsection 129 c, it is possible to increase injection efficiency forsecond carriers (e.g., holes) and reduce resistance, thereby improvingthe operating voltage Vf. However, the present disclosure is not limitedthereto, and the blocking layer 129 may not include a dopant. The firstsection 129 a may have an aluminum composition increasing toward thesecond conductive semiconductor layer 127. The region of highestaluminum composition in the first section 129 a may have an aluminumcomposition ranging from about 80% to about 100%. That is, the firstsection 129 a may be made of AlGaN or AlN. Alternatively, the firstsection 129 a may be a superlattice layer in which AlGaN and AlN arealternately provided.

The first section 129 a may have a thickness ranging from about 0.1 nmto about 4 nm. When the first section 129 a has a thickness of less thanabout 0.1 nm and/or when the region of highest aluminum composition inthe first section 129 a has an aluminum composition of less than 80%, itmay not be possible to efficiently block the movement of first carriers(e.g., electrons). Also, when the first section 129 a has a thicknessgreater than about 4 nm, it is possible for there to be a reduction inthe efficiency with which second carriers (e.g., holes) are injectedinto the active layer.

Together with the first section 129 a, the second section 129 c mayserve to efficiently block movement of the first carriers (e.g.,electrons). The second section 129 c may include a second dopant inorder to enhance injection of second carriers (e.g., holes). The seconddopant may include a p-type dopant such as Mg, Zn, Ca, Sr, and Ba. Thesecond section 129 c may have a thickness ranging from about 15 nm toabout 30 nm. When the thickness is less than about 15 nm, it may not bepossible to efficiently block movement of first carriers (e.g.,electrons). Also, when the thickness is greater than about 30 nm, it ispossible for there to be a reduction in the efficiency with which secondcarriers (e.g., holes) are injected into the active layer.

An undoped section 129 b, which is not doped with Mg, may be providedbetween the first section 129 a and the second section 129 c. Theundoped section 129 b may serve to prevent a dopant included in thesecond conductive semiconductor layer 127 from diffusing from the secondconductive semiconductor layer 127 to the active layer 126. The undopedsection 129 b may have a thickness ranging from about 10 nm to about 15nm. When the thickness is less than about 10 nm, it may be difficult toprevent a dopant from diffusing to the active layer 126. When thethickness is greater than about 15 nm, it is possible for there to be areduction in the efficiency with which second carriers (e.g., holes) areinjected.

The second conductive semiconductor layer 127 may include a conductivefirst semiconductor layer 127 a, a conductive second semiconductor layer127 b, and a conductive third semiconductor layer 127 c.

The conductive second semiconductor layer 127 b may have a thicknessgreater than about 10 nm and less than about 50 nm. For example, thesecond semiconductor layer 127 b may have a thickness equal to about 25nm. When the conductive second semiconductor layer 127 b has a thicknessless than about 10 nm, it is possible to reduce electric currentinjection efficiency because of a horizontal increase in resistance.When the conductive second semiconductor layer 127 b has a thicknessgreater than about 50 nm, it is possible for there to be a reduction inelectric current injection efficiency because of an increase inresistance in the horizontal direction.

The conductive second semiconductor layer 127 b may have a higheraluminum composition than the well layer 126 a. In order to generateultraviolet light, the well layer 126 a may have an aluminum compositionranging from about 30% to about 70%. When the conductive secondsemiconductor layer 127 b has a lower aluminum composition than the welllayer 126 a, it is possible for there to be a reduction in lightextraction efficiency because the conductive second semiconductor layer127 b absorbs light. However, the present disclosure is not limitedthereto. For example, in some sections, the conductive secondsemiconductor layer 127 b may have a lower aluminum composition than thewell layer 126 a.

The conductive second semiconductor layer 127 b may have an aluminumcomposition greater than about 40% and less than about 80%. When thealuminum composition of the conductive second semiconductor layer 127 bis less than about 40%, light may be absorbed. When the aluminumcomposition of the conductive second semiconductor layer 127 b isgreater than about 80%, electric current injection efficiency maydeteriorate. For example, when the well layer 126 a has an aluminumcomposition of about 30%, the conductive second semiconductor layer 127b may have an aluminum composition of about 40%.

The conductive first semiconductor layer 127 a may have a lower aluminumcomposition than the well layer 126 a. When the conductive firstsemiconductor layer 127 a has a higher aluminum composition than thewell layer 126 a, the conductive first semiconductor layer 127 a is notsufficiently ohmic with a second electrode due to an increase inresistance therebetween, and electric current injection efficiency isalso reduced.

The conductive first semiconductor layer 127 a may have an aluminumcomposition greater than about 1% and less than about 50%. When thealuminum composition is greater than about 50%, the conductive firstsemiconductor layer 127 a may not be sufficiently ohmic with the secondelectrode. When the aluminum composition is less than about 1%, thecomposition is close to GaN, and thus the conductive first semiconductorlayer 127 a absorbs light.

The conductive first semiconductor layer 127 a may have a thicknessranging from about 1 nm to about 30 nm or ranging from about 1 nm toabout 10 nm. As described above, the conductive first semiconductorlayer 127 a may absorb ultraviolet light because the conductive firstsemiconductor layer 127 a has an aluminum composition low enough to beohmic. Accordingly, it may be advantageous in terms of optical outputpower to control the conductive first semiconductor layer 127 a to be asthin as possible.

However, when the thickness of the conductive first semiconductor layer127 a is controlled to be less than or equal to about 1 nm, it ispossible for there to be a reduction in crystallinity due to a change inaluminum composition. Also, the conductive first semiconductor layer 127a is so thin that horizontal resistance of the conductive firstsemiconductor layer 127 a may increase and the electricalcharacteristics of the semiconductor device may decrease. Also, when thethickness is greater than about 30 nm, the absorbed light quantity islarge enough that optical output power efficiency may decrease.

The conductive first semiconductor layer 127 a may have a smallerthickness than the conductive second semiconductor layer 127 b. Thethickness ratio of the conductive second semiconductor layer 127 b tothe conductive first semiconductor layer 127 a may range from 1.5:1 to20:1. When the thickness ratio is less than 1.5:1, the conductive secondsemiconductor layer 127 is thin enough that the electric currentinjection efficiency may decrease. When the thickness ratio is greaterthan 20:1, the conductive first semiconductor layer 127 a is thin enoughthat crystallinity may be reduced and the electrical characteristics ofthe semiconductor device may be reduced.

The conductive second semiconductor layer 127 b may have an aluminumcomposition decreasing away from the active layer 126. Also, theconductive first semiconductor layer 127 a may have an aluminumcomposition decreasing away from the active layer 126.

In this case, the conductive first semiconductor layer 127 a may have agreater reduction in aluminum composition than the conductive secondsemiconductor layer 127 b. That is, the conductive first semiconductorlayer 127 a may have a greater variation in aluminum composition in thedirection of thickness than the conductive second semiconductor layer127 b.

The conductive second semiconductor layer 127 b is thicker than theconductive first semiconductor layer 127 a and has a higher aluminumcomposition than the well layer 126 a, and thus may have a relativelylow reduction in aluminum composition. However, since the conductivefirst semiconductor layer 127 a is thin and has a large change inaluminum composition, a reduction in aluminum composition may berelatively large. Since the conductive first semiconductor layer 127 ais thin and has a large change in aluminum composition, it is possibleto change the aluminum composition while relatively slowly growing theconductive first semiconductor layer 127 a.

The conductive third semiconductor layer 127 c may have a uniformaluminum composition. The conductive third semiconductor layer 127 c mayhave a thickness ranging from about 20 nm to about 60 nm. The conductivethird semiconductor layer 127 c may have an aluminum composition rangingfrom about 40% to about 70%. When the aluminum composition of theconductive third semiconductor layer 127 c is greater than or equal toabout 40%, it is possible for there to be a reduction in crystallinityof the conductive first semiconductor layer 127 a and the conductivesecond semiconductor layer 127 b. When the aluminum composition is lessthan about 70%, it is possible to prevent reduction of the crystallinitydue to a rapid change in aluminum composition of the conductive firstsemiconductor layer 127 a and the conductive second semiconductor layer127 b. Thus, it is possible to enhance the electrical characteristics ofthe semiconductor device.

As described above, the conductive first semiconductor layer 127 a mayhave a thickness ranging from about 1 nm to about 10 nm, the conductivesecond semiconductor layer 127 b may have a thickness ranging from about10 nm to about 50 nm, and the conductive third semiconductor layer 127 cmay have a thickness ranging from about 20 nm to about 60 nm.Accordingly, the ratio of the thickness of the conductive firstsemiconductor layer 127 a to the total thickness of the secondconductive semiconductor layer 127 may range from 1:3 to 1:120. When theratio is greater than 1:3, the conductive first semiconductor layer 127a may ensure the electrical characteristics (e.g., an operating voltage)of the semiconductor device. When the ratio is less than 1:120, theconductive first semiconductor layer 127 a may ensure the opticalcharacteristics (e.g., optical output power) of the semiconductordevice. However, the present disclosure is not limited thereto, and theratio of the thickness of the conductive first semiconductor layer 127 ato the total thickness of the second conductive semiconductor layer 127may range from 1:3 to 1:150 or range from 1:3 to 1:70.

FIG. 13 is a secondary ion mass spectrometry (SIMS) graph showing thechange in aluminum strength of the semiconductor structure according tothe third embodiment of the present disclosure, and FIG. 14 is apartially enlarged view of FIG. 13.

Referring to FIGS. 13 and 14, the semiconductor structure may havealuminum ion strength that changes from the first conductivesemiconductor layer 124 to the second conductive semiconductor layer127.

SIMS data may be analyzed through Time-of-Flight secondary ion massspectrometry (TOF-SIMS).

SIMS data may be analyzed by emitting primary ions to a target surfaceand counting the number of secondary ions discharged. In this case, theprimary ions may be selected from among O₂ ⁺, Cs⁺, Bi⁺, and so on, anacceleration voltage may be adjusted between the range of about 20 keVto about 30 KeV, an emitted current may be adjusted between the range ofabout 0.1 pA to about 5.0 pA, and a target area may be 20 nm×20 nm.

SIMS data may be obtained by collecting a secondary ion mass spectrumwhile gradually etching a surface of the second conductive semiconductorlayer in a direction toward the first conductive semiconductor layer.Here, the secondary ions may each be an aluminum ion. In this case, aspectrum of aluminum ion strength may be expressed on a linear scale,but the present disclosure is not limited thereto. The spectrum may alsobe expressed on a log scale.

The semiconductor structure may have a first point P1 with the lowestaluminum ion strength in the first conductive semiconductor layer 124, asecond point P2 with the highest aluminum ion strength in the blockinglayer, and a third point P3 with the lowest aluminum ion strength in thesecond conductive semiconductor layer 127. However, the presentdisclosure is not limited thereto, and the point of highest aluminum ionstrength and the point of lowest aluminum ion strength in thesemiconductor structure may be different from those described above.

The first point P1 may be positioned in the intermediate layer 124 bthat is provided in the first conductive semiconductor layer, and may bea region that is in contact with the first electrode 142. The secondpoint P2 may be positioned in the first section 129 a of the blockinglayer 129. The third point P3 may be positioned in a contact layer (theconductive first semiconductor layer) where the second conductivesemiconductor layer is in direct contact with the second electrode (aP-ohmic electrode).

When the first point P1, the second point P2, and the third point P3 aremeasured through SIMS, a semiconductor layer of a certain thickness orgreater may include noise. For example, the first point P1 may bedefined as a layer having the same strength as a layer having lowaluminum ion strength in the first conductive semiconductor layer. Inthis case, noise at the first point P1 may be 2% or less of thedifference between the high point and the low point

The ratio of the difference in aluminum strength between the first pointP1 and the second point P2, called D1, to the difference in aluminumstrength between the first point P1 and the third point P3, called D2,(i.e., D1:D2) may range from 1:0.2 to 1:2.

When the ratio is greater than 1:0.2 , it is possible to sufficientlyensure the second aluminum strength difference D2, thus improvingcontact resistance between the second conductive semiconductor layer andthe second electrode.

When the ratio is less than or equal to 1:2, by preventing a relativeincrease in the second aluminum strength difference D2, it is possibleto adjust the change in aluminum strength with respect to the thicknessof the conductive first semiconductor layer 127 a such that the changedoes not become too large Accordingly, it is possible to improvecrystallinity of the semiconductor structure and improve transmittanceof the conductive first semiconductor layer 127 a with respect to lightemitted by the active layer 126 to enhance the optical characteristicsof the semiconductor device.

On the other hand, when a thin GaN layer (a surface layer) is insertedfor the purpose of ohmic contact between the second conductivesemiconductor layer and an electrode, the GaN layer that is in contactwith the electrode does not include aluminum. Thus it is possible torapidly increase the second aluminum strength difference D2.Accordingly, the ratio of the first aluminum strength difference D1 tothe second aluminum strength difference D2 (D1:D2) may depart from therange of 1:0.2 to 1:2.

The ratio between the first thickness W1 of the semiconductor structureto the second thickness W2 of the semiconductor (W1:W2) may range from1:0.2 to 1:1. The first thickness W1 may be the thickness of thesemiconductor structure between a fourth point P1 and a second point P2positioned in the second conductive semiconductor layer 127, and thesecond thickness W2 may be the thickness of the semiconductor structurebetween the fourth point P1 and a third point P3 positioned in thesecond conductive semiconductor layer 127.

When the ratio of the first thickness W1 to the second thickness W2(W1:W2) is greater than or equal to 1:0.2 , it is possible to improvecrystallinity by ensuring the second thickness W2.

Also, when the thickness ratio is less than or equal to 1:1, it ispossible to relatively reduce the second thickness W2. Accordingly, itis possible to improve light extraction efficiency by alleviating theproblem of light emitted by the active layer 126 being absorbed insidethe second thickness W2.

Referring to FIG. 15, a first conductive semiconductor layer 124, anactive layer 126, a blocking layer 129, and a second conductivesemiconductor layer 127 may be sequentially stacked on the semiconductorstructure. A second electrode may be brought in direct contact with thesurface 127 a of the second conductive semiconductor layer 127 to forman ohmic contact.

FIG. 16 is a diagram of the second conductive semiconductor layer ofFIG. 1, FIG. 17 shows AFM data obtained by measuring the surface of thesecond conductive semiconductor layer according to the third embodimentof the present disclosure, FIG. 18 shows AFM data obtained by measuringthe surface of a GaN thin film, and FIG. 19 shows AFM data obtained bymeasuring the surface of a fast-grown second conductive semiconductorlayer.

Referring to FIG. 18, a second conductive semiconductor layer 127according to an embodiment of the present disclosure may include a 2-1conductive semiconductor layer 127 a, a conductive second semiconductorlayer 127 b, and a conductive third semiconductor layer 127 c. Theconductive first semiconductor layer 127 a may be a contact layer thatis in contact with the second electrode. As features of the layers, theabove-description may be applied as it is.

The surface of the conductive first semiconductor layer 127 a mayinclude a plurality of clusters C1. Each of the clusters C1 may be aprotrusion protruding from the surface. For example, each of theclusters C1 may be a protrusion protruding more than about 10 nm or 20nm from the average surface height. Each of the clusters C1 may beformed due to a lattice mismatch between aluminum Al and gallium Ga.

The conductive first semiconductor layer 127 a includes aluminum, has alarge variation in thickness of aluminum, and is thinner than otherlayers. Thus, the surface may be formed not in a single layer but in theform of clusters C1. Each of the clusters C1 may include Al, Ga, N, Mg,or the like. However, the present disclosure is not limited thereto.

Referring to FIG. 17, clusters C1 formed in the shape of relativelybright dots may be seen from the surface of the second conductivesemiconductor layer 127. According to an embodiment of the presentdisclosure, since the conductive first semiconductor layer 127 a has analuminum composition ranging from about 1% to about 10%, the surface maybe generated in the form of clusters C1 to increase contact area.Accordingly, it is possible to enhance electrical characteristics.

100 to 800 clusters C1 may be observed per average 100 μm² in thesurface of the second conductive semiconductor layer 127. Here, theaverage value is the average of values measured at about 10 or moredifferent positions. The result obtained by measuring position E1 ofFIG. 17 was 12 clusters C1 observed per unit area, which is 2 μm×2 μm.Only clusters protruding more than 25 nm from the surface were measuredas the clusters C1. By adjusting contrast in an AFM image, it ispossible to ensure that only clusters protruding more than 25 nm fromthe surface may be output.

The clusters C1, using converted units based on the measurement results,may have a density ranging from 1×10⁻⁸/cm² to 8×10⁻⁶/cm². When thedensity of the clusters C1 is greater than or equal to 1×10⁻⁸/cm², thecontact area may relatively increase, and contact resistance with thesecond electrode may decrease.

Also, when the density of the clusters C1 is less than or equal to8×10⁻⁶/cm², it is possible to alleviate the problem of light emitted bythe active layer 126 being absorbed by Ga included in some of theclusters. Accordingly, it is possible to improve optical output power.

According to an embodiment of the present disclosure, the density of theclusters C1 may satisfy 1×10⁻⁸/cm² to 8×10⁻⁶/cm², and thus it ispossible to decrease contact resistance with the second electrode whilenot reducing the optical output power.

Referring to FIG. 18, it can be seen that no cluster was observed fromthe surface of a GaN thin film. This is because the surface is formed ina single layer as the density of the clusters increases. Accordingly, itcan be seen that no cluster is formed on the contact surface when a GaNthin film is formed between the second conductive semiconductor layerand the second electrode. Accordingly, when a GaN-based semiconductormaterial including aluminum such as AlGaN is provided on the surface ofthe semiconductor structure, the clusters C1 may be formed on thesurface of the semiconductor structure.

Referring to FIG. 19, it can be seen that clusters are not grown wellwhen the second conductive semiconductor layer is fast-grown.Accordingly, it can be seen that no clusters C1 are formed when thesecond conductive semiconductor layer is fast-grown although the secondconductive semiconductor layer is controlled such that the aluminumcomposition of the surface of the second conductive semiconductor layerranges from about 1% to about 10%. For example, FIG. 19 is a photographobtained by measuring the surface after P—AlGaN is grown at a speed of0.06 nm/s.

That is, it can be seen that a contact layer should have an aluminumcomposition ranging from about 1% to about 10% and also a sufficientlylow growth speed in order to form a plurality of clusters C1 in thesecond conductive semiconductor layer 127.

According to an embodiment of the present disclosure, the conductivefirst semiconductor layer may have a lower growth speed than theconductive second semiconductor layer and the conductive thirdsemiconductor layer. For example, the ratio of the growth speed of theconductive second semiconductor layer and the conductive firstsemiconductor layer may range from 1:0.2 to 1:0.8. When the growth speedratio is less than 1:0.2, the growth speed of the conductive firstsemiconductor layer is so low that AlGaN having a high aluminumcomposition may be grown by Ga being etched at the same high temperatureat which the AlGaN is grown, and thus reducing ohmic characteristics.When the growth speed ratio is greater than 1:0.8, the growth speed ofthe conductive first semiconductor layer is so high that thecrystallinity may be reduced. FIG. 20 is a diagram of a semiconductordevice according to the third embodiment of the present disclosure, FIG.21A is a plan view of FIG. 20, FIG. 21B is a view enlarging a portion Aof FIG. 20, and FIG. 22 is a plan view illustrating a portion of aninterface between the second conductive semiconductor layer and thesecond electrode.

Referring to FIG. 20, a semiconductor structure 120 may have aconfiguration of the above-described semiconductor structure 120 appliedas it is. A plurality of recesses 128 may be provided even in a portionof a first conductive semiconductor layer 124 through a secondconductive semiconductor layer 127 and an active layer 126.

The semiconductor device may include a side reflector Z1 provided on anedge thereof. The side reflector Z1 may be formed by a second conductivelayer 150, a first conductive layer 165, and a substrate 170 protrudingin the direction of thickness (a y-axis direction). Referring to FIG.21A, the side reflector Z1 may be provided along the edge of thesemiconductor device to surround the semiconductor structure.

The second conductive layer 150 of the side reflector Z1 protrudesfurther than the active layer 126 so that the second conductive layer150 may upwardly reflect light L2 emitted by the active layer 126.Accordingly, without a separate reflective layer being formed, it ispossible to reflect light emitted in a horizontal direction (an x-axisdirection) upward at the outermost portion because of the TM mode.

The side reflector Z1 may have a slope angle greater than about 90degrees and less than about 145 degrees. The slope angle may be an anglebetween the second conductive layer 150 and the horizontal plane (an XZplane). When the angle is less than about 90 degrees or greater thanabout 145 degrees, it is possible for there to be a reduction in theefficiency with which light traveling toward the side is reflectedupward.

Referring to FIG. 21B, a second electrode 246 may be in direct contactwith a 2-1 conductive semiconductor layer 127 a. As described above,clusters may be provided on the surface of the 2-1 conductivesemiconductor layer 127 a to increase contact area with the secondelectrode 246.

The second electrode 246 may be deposited on the conductive firstsemiconductor layer 127 a. When the second electrode is made of a metaloxide such as ITO, the conductive first semiconductor layer 127 a maycome in contact with oxygen. Accordingly, an aluminum oxide may beformed by aluminum that is provided on the surface of the conductivefirst semiconductor layer 127 a to react with oxygen. In addition, anitride such as NO and an oxide such as Ga₂O₃ may be additionallyformed.

Referring to FIG. 22, an aluminum oxide C2 may be observed at aninterface between the second electrode 246 and the conductive firstsemiconductor layer 127 a. The interface may be observed using atransmission electron microscope (TEM).

FIG. 23 is a diagram of a semiconductor device package according to anembodiment of the present disclosure, FIG. 24 is a plan view of thesemiconductor device package according to an embodiment of the presentdisclosure, and FIG. 25 is a modification of FIG. 24.

Referring to FIG. 23, the semiconductor device package may include abody 2 with a groove (an opening) 3, a semiconductor device 1 providedin the body 2, and a pair of lead frames 5 a and 5 b provided in thebody 2 and electrically connected to the semiconductor device 1. Thesemiconductor device 1 may include all of the above-described elements.

The body 2 may include a material or a coating layer that reflectsultraviolet light. The body 2 may be formed by stacking a plurality oflayers 2 a, 2 b, 2 c, 2 d, and 2 e. The plurality of layers 2 a, 2 b , 2c, 2 d, and 2 e may be made of the same material or include differentmaterials. For example, the plurality of layers 2 a, 2 b , 2 c, 2 d, and2 e may include an aluminum material.

The groove 3 may have a width that increases away from the semiconductordevice and may have an inclined surface having a stepped portion formedtherein.

A light transmitting layer 4 may cover the groove 3. The lighttransmitting layer 4 may be made of glass, but is not limited thereto.There is no limitation in material of the light transmitting layer 4 aslong as the material can effectively transmit ultraviolet light. Thegroove 3 may have an empty space formed therein.

Referring to FIG. 24, a semiconductor device 10 may be provided on afirst lead frame 5 a and connected with a second lead frame 5 b by usinga wire. In this case, the second lead frame 5 b may be provided tosurround the first lead frame 5 a.

Referring to FIG. 25, the semiconductor device package may have aplurality of semiconductor devices 10 a, 10 b, 10 c, and 10 d providedtherein. In this case, the lead frame may include a first lead frame 5a, a second lead frame 5 b, a third lead frame 5 c, a fourth lead frame5 d, and a fifth lead frame 5 e.

The first semiconductor device 10 a may be provided on the first leadframe 5 a and connected with the second lead frame 5 b using a wire. Thesecond semiconductor device 10 b may be provided on the second leadframe 5 b and connected with the third lead frame 5 c by using a wire.The third semiconductor device 10 c may be provided on the third leadframe 5 c and connected with the fourth lead frame 5 d using a wire. Thefourth semiconductor device 10 d may be provided on the fourth leadframe 5 d and connected with the fifth lead frame 5 e using a wire.

The semiconductor device may be applied to various kinds of light sourcedevices. For example, the light source devices may include a sterilizingdevice, a curing device, a lighting device, a display device, and avehicle lamp. That is, the semiconductor device may be applied invarious electronic devices provided in a housing and configured toprovide light.

The sterilizing device may have a semiconductor device to sterilize adesired region according to an embodiment of the present disclosure. Thesterilizing device may be applied to home appliances such as a waterpurifiers, air conditioners, and refrigerators, but is not limitedthereto. That is, the sterilizing device may be applied in variousproducts needing to be sterilized (e.g., medical apparatuses).

For example, a water purifier may have the sterilizing device tosterilize circulating water according to an embodiment of the presentdisclosure. The sterilizing device may be placed at a nozzle or adischarging port through which water circulates and configured to emitultraviolet light. In this case, the sterilizing device may include awaterproof structure.

The curing device may have a semiconductor device to cure various kindsof liquids according to an embodiment of the present disclosure. Theliquids may include various materials that are cured when ultravioletlight is emitted. For example, the curing device may cure various typesof resins. Alternatively, the curing device may also be applied to curebeauty products such as manicure products.

The lighting device may, according to an embodiment of the presentdisclosure, include a light source module including a substrate and asemiconductor device, a heat dissipation unit configured to dissipateheat of the light source module, and a power supply unit configured toprocess or convert an electric signal from the outside and provide theelectric signal to the light source module. Also, the lighting devicemay include a lamp, a headlamp, or a streetlight.

The display device may include a bottom cover, a reflective plate, alight emitting module, a light guide plate, an optical sheet, a displaypanel, an image signal output circuit, and a color filter. The bottomcover, the reflective plate, the light emitting module, the light guideplate, and the optical sheet may constitute a backlight unit.

The reflective plate may be placed on the bottom cover, and the lightemitting module may emit light. The light guide plate may be placed infront of the reflective plate to guide light emitted by the lightemitting module forward. The optical sheet may include a prism sheet orthe like and may be placed in front of the light guide plate. Thedisplay panel may be placed in front of the optical sheet. The imagesignal output circuit may supply an image signal to the display panel.The color filter may be placed in front of the display panel.

When the semiconductor device is used as a backlight unit of a displaydevice, the semiconductor device may be used as an edge-type backlightunit or a direct-type backlight unit.

The semiconductor device may be a laser diode rather than theabove-described light emitting diode.

Like the light emitting device, the laser diode may include a firstconductive semiconductor layer, an active layer, and a second conductivesemiconductor layer that have the above-described structures. The laserdiode may also utilize an electroluminescence phenomenon in which lightis emitted when electric current flows after a p-type first conductivesemiconductor and an n-type second conductive semiconductor are broughtin contact with each other, but has a difference in the directionalityand phase of the emitted light. That is, the laser diode uses stimulatedemission and constructive interference so that light having a specificsingle wavelength may be emitted at the same phase and in the samedirection. Due to these characteristics, the laser diode may be used foran optical communication device, a medical device, a semiconductorprocessing device, or the like.

A light receiving device may include, for example, a photodetector,which is a kind of transducer configured to detect light and convertintensity of the light into an electric signal. The photodetector mayinclude a photocell (silicon and selenium), an optical output element(cadmium sulfide and cadmium selenide), a photodiode (e.g., a PD with apeak wavelength in a visible blind spectral region or a true blindspectral region), a photo transistor, a photomultiplier, a photoelectrictube (vacuum and gas filling), an infra-red (IR) detector, or the like,but is not limited thereto.

Generally, a semiconductor device such as the photodetector may beproduced using a direct bandgap semiconductor having good photoelectrictransformation efficiency. Alternatively, the photodetector may havevarious structures. As the most common structure, the photodetector mayinclude a pin-type photodetector using a p-n junction, a Schottkyphotodetector using a Schottky junction, a metal-semiconductor-metal(MSM) photodetector, or the like.

Like the light emitting device, the photodiode may include a firstconductive semiconductor layer and a second conductive semiconductorlayer that have the above-described structures and may be formed as ap-n junction or a pin structure. The photodiode operates when a reversebias or a zero bias is applied. When light is incident on thephotodiode, electrons and holes are generated such that electric currentflows. In this case, the magnitude of electric current may beapproximately proportional to intensity of light incident on thephotodiode.

A photocell or a solar cell, which is a kind of photodiode, may convertlight into electric current. Like the light emitting device, the solarcell may include a first conductive semiconductor layer, an activelayer, and a second conductive semiconductor layer that have theabove-described structures.

Also, the solar cell may be used as a rectifier of an electronic circuitthrough the rectification characteristics of a general diode using a p-njunction and may be applied to an oscillation circuit or the like of amicrowave circuit.

Also, the above-described semiconductor device is not necessarilyimplemented only with semiconductors. Depending on the case, thesemiconductor device may additionally include a metal material. Forexample, a semiconductor device such as the light receiving device maybe implemented using at least one of Ag, Al, Au, In, Ga, N, Zn, Se, P,and As and may be implemented using an intrinsic semiconductor materialor a semiconductor material doped with a p-type dopant or an n-typedopant.

Depending on the embodiments of the present disclosure, it is possibleto produce a vertical ultraviolet light emitting device.

Also, it is possible to enhance optical output power by suppressingabsorption of light in the semiconductor device.

Also, it is possible to reduce contact resistance between the secondconductive semiconductor layer and the second electrode without a GaNthin film.

Various advantages and effects of the present disclosure are not limitedto the above description and may be more easily understood while theembodiments of the present disclosure are described in detail.

While the present disclosure has been described with reference toexemplary embodiments, these are just examples and do not limit thepresent disclosure. It will be understood by those skilled in the artthat various modifications and applications may be made therein withoutdeparting from the essential characteristics of the embodiments. Forexample, elements described in the embodiments above in detail may bemodified and implemented. Furthermore, differences associated with suchmodifications and applications should be construed as being included inthe scope of the present disclosure defined by the appended claims.

An embodiment provides a vertical ultraviolet light emitting device.

An embodiment also provides a light emitting device having enhancedoptical output power.

Problems to be solved in the embodiments are not limited thereto, andinclude the following technical solutions and objectives or effectsunderstandable from the embodiments.

According to an aspect of the present disclosure, there is provided asemiconductor device including a semiconductor structure including afirst conductive semiconductor layer, a second conductive semiconductorlayer, and an active layer provided between the first conductivesemiconductor layer and the second conductive semiconductor layer. Theactive layer may include a plurality of barrier layers and a pluralityof well layers. The second conductive semiconductor layer may include a2-2 conductive semiconductor layer and a 2-1 conductive semiconductorlayer provided on the 2-2 conductive semiconductor layer. The barrierlayers, the well layers, the 2-2 conductive semiconductor layer, and the2-1 conductive semiconductor layer may include AlGaN. The 2-2 conductivesemiconductor layer may have a higher aluminum composition than the welllayers, and the 2-1 conductive semiconductor layer may have a loweraluminum composition than the well layers.

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the disclosure. Theappearances of such phrases in various places in the specification arenot necessarily all referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with any embodiment, it is submitted that it is within thepurview of one skilled in the art to effect such feature, structure, orcharacteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

What is claimed is:
 1. A semiconductor device comprising: a firstconductive semiconductor layer; a second conductive semiconductor layer;and an active layer provided between the first conductive semiconductorlayer and the second conductive semiconductor layer, wherein: the activelayer comprises a plurality of barrier layers and a plurality of welllayers; the second conductive semiconductor layer includes a conductivefirst semiconductor layer and a conductive second semiconductor layer,and the conductive first semiconductor layer provided on the conductivesecond semiconductor layer; the barrier layers, the well layers, theconductive second semiconductor layer, and the conductive firstsemiconductor layer include aluminum; the conductive secondsemiconductor layer has a higher aluminum composition than the pluralityof well layers; the conductive first semiconductor layer has a loweraluminum composition than the plurality of well layers; the aluminumcomposition of the conductive first semiconductor layer decreases in afirst concentration gradient as the conductive first semiconductor isfurther away from the active layer; the aluminum composition of theconductive second semiconductor layer decreases in a secondconcentration gradient as the conductive second semiconductor layer isfurther away from the active layer; and a rate of decrease of the firstconcentration gradient is greater than a rate of decrease of the secondconcentration gradient.
 2. The semiconductor device of claim 1, whereinthe first conductive semiconductor layer comprises a conductive firstsemiconductor layer, a conductive second semiconductor layer, and anintermediate layer provided between the conductive first semiconductorlayer and the conductive second semiconductor layer, wherein theintermediate layer has a lower aluminum composition than the conductivefirst semiconductor layer and the conductive second semiconductor layerof the first conductive semiconductor layer.
 3. The semiconductor deviceof claim 2, wherein the intermediate layer has a higher aluminumcomposition than the plurality of well layers.
 4. The semiconductordevice of claim 1, wherein the active layer emits light of anultraviolet wavelength band.
 5. The semiconductor device of claim 1,wherein the conductive second semiconductor layer has an aluminumcomposition greater than 40% and less than 80%.
 6. The semiconductordevice of claim 5, wherein the conductive second semiconductor layer hasa thickness greater than 10 nm and less than 20 nm.
 7. The semiconductordevice of claim 1, wherein the conductive first semiconductor layer hasan aluminum composition greater than 1% and less than 50%.
 8. Thesemiconductor device of claim 1, wherein the conductive firstsemiconductor layer has a thickness greater than 1 nm and less than 30nm.
 9. The semiconductor device of claim 1, wherein the conductive firstsemiconductor layer has a smaller thickness than the conductive secondsemiconductor layer.
 10. The semiconductor device of claim 1, furthercomprising a plurality of recesses arranged even in prescribed regionsof the first conductive semiconductor layer through the secondconductive semiconductor layer and the active layer.
 11. Thesemiconductor device of claim 10, further comprising a connectionelectrode provided in the plurality of recesses and electricallyconnected to the first conductive semiconductor layer.
 12. Thesemiconductor device of claim 11, further comprising: a first electrodeprovided between the first conductive semiconductor layer and theconnection electrode; and a second electrode electrically connected tothe conductive first semiconductor layer.
 13. The semiconductor deviceof claim 12, wherein: the conductive first semiconductor layer comprisesa surface layer that is in contact with the second electrode; and thesurface layer has an aluminum composition ranging from 1% to 20%. 14.The semiconductor device of claim 1, further comprising a thirdconductive semiconductor layer provided on the second conductivesemiconductor layer; the third conductive semiconductor layer has alower aluminum composition than the well layers; the first and thirdconductive semiconductor layer include an n-type dopant; and the secondconductive semiconductor layer includes a p-type dopant.
 15. Thesemiconductor device of claim 14, wherein the aluminum composition ofthe third conductive semiconductor layer is greater than 1% and lessthan 60%.
 16. The semiconductor device of claim 15, wherein the thirdconductive semiconductor layer has a thickness less than 10 nm.
 17. Thesemiconductor device of claim 16, wherein the second conductivesemiconductor layer has an aluminum composition that decreases away fromthe active layer.
 18. The semiconductor device of claim 14, wherein thethird conductive semiconductor layer has a smaller thickness than thesecond conductive semiconductor layer.
 19. The semiconductor device ofclaim 14, further comprising a second electrode that is in contact withthe third conductive semiconductor layer; and the second electrodeincludes an ITO.
 20. A semiconductor device package comprising: a body;and a semiconductor device provided in the body, wherein: thesemiconductor device includes: a first conductive semiconductor layer; asecond conductive semiconductor layer; and an active layer providedbetween the first conductive semiconductor layer and the secondconductive semiconductor layer; the active layer includes a plurality ofbarrier layers and a plurality of well layers; the second conductivesemiconductor layer includes a conductive first semiconductor layer anda conductive second semiconductor layer and the conductive firstsemiconductor layer being provided on the conductive secondsemiconductor layer; the barrier layers, the well layers, the conductivesecond semiconductor layer, and the conductive first semiconductor layerinclude AlGaN; the conductive second semiconductor layer has a higheraluminum composition than the well layers; the conductive firstsemiconductor layer has a lower aluminum composition than the welllayers; the aluminum composition of the conductive first semiconductorlayer decreases in a first concentration gradient in a thicknessdirection of the conductive first semiconductor layer away from theactive layer; the aluminum composition of the conductive secondsemiconductor layer decreases in a second concentration gradient in athickness direction ofthe conductive second semiconductor layer awayfrom the active layer; and a rate of decrease of the first concentrationgradient is greater than a rate of decrease of the second concentrationgradient.